Janus complementary MEMS transistors and circuits

ABSTRACT

A method of fabricating an electromechanical device includes the following steps. A first and a second back gate are formed over a substrate. An etch stop layer is formed covering the first and second back gates. Electrodes are formed over the first and second back gates, wherein the electrodes include one or more gate, source, and drain electrodes, wherein gaps are present between the source and drain electrodes. One or more Janus components are placed the gaps, each of which includes a first portion having an electrically conductive material and a second portion having an electrically insulating material, and wherein i) the first or second portion of the Janus components placed in a first one of the gaps has a fixed positive surface charge and ii) the first or second portion of the Janus components placed in a second one of the gaps has a fixed negative surface charge.

FIELD OF THE INVENTION

The present invention relates to electromechanical devices, and moreparticularly, to transistors and circuits that employ complementaryJanus micro/nano-components (e.g., Janus particles, cylinders, prisms,etc.) and techniques for the fabrication thereof.

BACKGROUND OF THE INVENTION

Microelectromechanical (MEMS) and nanoelectromechanical (NEMS) deviceshave been implemented in a number of different applications, such asrelays. Because they are mechanical, MEMS and NEMS can reduce standbyleakage current. Electromechanical devices also potentially have bettersub-threshold behavior than transistors (which are limited by 60mV/dec.).

Relays need to have low switching voltage and high endurance. However,many conventional MEMS and NEMS devices rely on a cantilever designwherein a cantilever structure (e.g., a polysilicon arm or array ofarms) actuates during operation of the device. Thus the reliability ofthese conventional devices can be an issue. Reliability refers to alifetime of the electromechanical switch, for example how many times theelectromechanical transistor can be switched on and off, how long theelectromechanical transistor can stay on with resistance less than acertain value, etc.

Therefore, an improved electromechanical device that does not sufferfrom the above-described drawbacks would be desirable.

SUMMARY OF THE INVENTION

The present invention provides transistors and circuits that employcomplementary Janus micro/nano-components (e.g., Janus particles,cylinders, prisms, etc.) and techniques for the fabrication thereof. Inone aspect of the invention, a method of fabricating anelectromechanical device is provided. The method includes the followingsteps. A first back gate and a second back gate are formed on a firstdielectric layer over a substrate. An etch stop layer is formed coveringthe first back gate and a second back gate. Electrodes are formed in asecond dielectric layer on the etch stop layer over the first back gateand the second back gate, wherein the electrodes include one or moregate electrodes, one or more source electrodes and one or more drainelectrodes, wherein gaps are present between the source electrodes andthe drain electrodes, and wherein the gate electrodes are locatedadjacent to the gaps, perpendicular to the source and drain electrodes.One or more Janus components are placed in each of the gaps between thesource and drain electrodes, wherein each of the Janus componentsincludes a first portion having an electrically conductive material anda second portion having an electrically insulating material, and whereini) either the first portion or the second portion of the Januscomponents placed in a first one of the gaps has a fixed positivesurface charge and ii) either the first portion or the second portion ofthe Janus components placed in a second one of the gaps has a fixednegative surface charge.

In another aspect of the invention, an electromechanical device isprovided. The device includes: a first back gate and a second back gateon a first dielectric layer over a substrate; an etch stop layercovering the first back gate and a second back gate; electrodes formedin a second dielectric layer on the etch stop layer over the first backgate and the second back gate, wherein the electrodes include one ormore gate electrodes, one or more source electrodes and one or moredrain electrodes, wherein gaps are present between the source electrodesand the drain electrodes, and wherein the gate electrodes are locatedadjacent to the gaps, perpendicular to the source and drain electrodes;and one or more Janus components placed in each of the gaps between thesource and drain electrodes, wherein each of the Janus componentsincludes a first portion having an electrically conductive material anda second portion having an electrically insulating material, and whereini) either the first portion or the second portion of the Januscomponents placed in a first one of the gaps has a fixed positivesurface charge and ii) either the first portion or the second portion ofthe Janus components placed in a second one of the gaps has a fixednegative surface charge.

In yet another aspect of the invention, a method of operating anelectromechanical device is provided. The method includes the followingsteps. The electromechanical device is provided. The electromechanicaldevice includes a first back gate and a second back gate on a firstdielectric layer over a substrate; an etch stop layer covering the firstback gate and a second back gate; electrodes formed in a seconddielectric layer on the etch stop layer over the first back gate and thesecond back gate, wherein the electrodes comprise one or more gateelectrodes, one or more source electrodes and one or more drainelectrodes, wherein gaps are present between the source electrodes andthe drain electrodes, and wherein the gate electrodes are locatedadjacent to the gaps, perpendicular to the source and drain electrodes;and one or more Janus components placed in each of the gaps between thesource and drain electrodes, wherein each of the Janus componentsincludes a first portion having an electrically conductive material anda second portion having an electrically insulating material, and whereini) either the first portion or the second portion of the Januscomponents placed in a first one of the gaps has a fixed positivesurface charge and ii) either the first portion or the second portion ofthe Janus components placed in a second one of the gaps has a fixednegative surface charge. A gate voltage is applied to the gateelectrodes to move the Janus components so as to position either: a) thefirst portion of the Janus components placed in the first one of thegaps between a first set of the source and drain electrodes and thesecond portion of the Janus components placed in the second one of thegaps between a second set of the source and drain electrodes, or b) thesecond portion of the Janus components placed in the first one of thegaps between the first set of the source and drain electrodes and thefirst portion of the Janus components placed in the second one of thegaps between the second set of the source and drain electrodes.

A more complete understanding of the present invention, as well asfurther features and advantages of the present invention, will beobtained by reference to the following detailed description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a three-dimensional diagram illustrating an exemplary Janusparticle which may be used in accordance with the present techniquesaccording to an embodiment of the present invention;

FIG. 1B is a three-dimensional diagram illustrating an exemplary Januscylinder which may be used in accordance with the present techniquesaccording to an embodiment of the present invention;

FIG. 1C is a three-dimensional diagram illustrating another exemplaryJanus cylinder which may be used in accordance with the presenttechniques according to an embodiment of the present invention;

FIG. 1D is a three-dimensional diagram illustrating an exemplary Janusprism which may be used in accordance with the present techniquesaccording to an embodiment of the present invention;

FIG. 2 is a diagram illustrating a molecule containing hydroxamic groupsand bearing negatively charged (pyridine) groups being used to create afixed negative charge on the surface of the dielectric portions of theJanus components according to an embodiment of the present invention;

FIG. 3 is a diagram illustrating a molecule containing hydroxamic groupsand bearing positively charged (diazonium) groups being used to create afixed positive charge on the surface of the dielectric portions of theJanus components according to an embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating an exemplary relay devicehaving complementary Janus components according to an embodiment of thepresent invention;

FIG. 5 is a cross-sectional diagram illustrating a starting structurefor fabricating a complementary Janus component device wherein backgates of the device are formed in a dielectric on a substrate accordingto an embodiment of the present invention;

FIG. 6 is a cross-sectional diagram illustrating an etch stop layerhaving been formed over and covering the back gates according to anembodiment of the present invention;

FIG. 7 is a cross-sectional diagram illustrating electrodes having beenformed over the back gates according to an embodiment of the presentinvention;

FIG. 8 is a top-down diagram illustrating an exemplary configuration ofthe electrodes (i.e., including source, drain and gate electrodes)forming a single input/output inverter device according to an embodimentof the present invention;

FIG. 9 is a top-down diagram illustrating another exemplaryconfiguration of the electrodes (i.e., including source, drain and gateelectrodes) in this case forming a double input/out inverter deviceaccording to an embodiment of the present invention;

FIG. 10 is a top-down diagram illustrating yet another exemplaryconfiguration of the electrodes (i.e., including source, drain and gateelectrodes) forming another single input/output inverter deviceaccording to an embodiment of the present invention;

FIG. 11 is a cross-sectional diagram illustrating anchor trenches havingbeen formed in the dielectric layer between the (source and drain)electrodes according to an embodiment of the present invention;

FIG. 12 is a cross-sectional diagram illustrating Janus components beingplaced in the n-type transistor using a ‘chemical approach’ wherein thedevice is contacted with a first aqueous solution containing positivelycharged Janus components, while a negative gate voltage (V<0) is appliedto one of the back gates according to an embodiment of the presentinvention;

FIG. 13 is a cross-sectional diagram illustrating the chemical approachbeing used to place negatively charged Janus components in the p-typetransistor from a second aqueous solution containing negatively chargedJanus components, while a positive gate voltage (V<0) is applied to theother of the back gates according to an embodiment of the presentinvention;

FIG. 14 is a cross-sectional diagram illustrating an optional liquidcoating having been deposited over/surrounding the device, covering theJanus components according to an embodiment of the present invention;

FIG. 15A is a top-down diagram illustrating operation of the singleinput/output electrode configuration of FIG. 8 when a positive gatevoltage is applied according to an embodiment of the present invention;

FIG. 15B is a top-down diagram illustrating operation of the singleinput/output electrode configuration of FIG. 8 when a negative gatevoltage is applied according to an embodiment of the present invention;

FIG. 16A is a top-down diagram illustrating operation of the doubleinput/output electrode configuration of FIG. 9 when a positive gatevoltage is applied according to an embodiment of the present invention;

FIG. 16B is a top-down diagram illustrating operation of the doubleinput/output electrode configuration of FIG. 9 when a negative gatevoltage is applied according to an embodiment of the present invention;

FIG. 17A is a top-down diagram illustrating operation of the singleinput/output electrode configuration of FIG. 10 when a positive gatevoltage is applied according to an embodiment of the present invention;

FIG. 17B is a top-down diagram illustrating operation of the singleinput/output electrode configuration of FIG. 10 when a negative gatevoltage is applied according to an embodiment of the present invention;

FIG. 18 is a cross-sectional diagram illustrating multiple Janusparticles connected in series in each (n-type or p-type) transistoraccording to an embodiment of the present invention;

FIG. 19 is a cross-sectional diagram illustrating multiple Janusparticles connected in parallel in each (n-type or p-type) transistoraccording to an embodiment of the present invention;

FIG. 20 is a diagram illustrating operation of the present complementaryJanus component devices where the Janus components are the Januscylinders of FIG. 1C according to an embodiment of the presentinvention;

FIG. 21 is a diagram illustrating operation of the present complementaryJanus component devices where the Janus components are the Januscylinders of FIG. 1B according to an embodiment of the presentinvention; and

FIG. 22 is a diagram illustrating operation of the present complementaryJanus component devices where the Janus components are the Janus prismsof FIG. 1D according to an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Provided herein are complementary electromechanical devices (e.g.,transistors) and circuits for ultra-low-power (i.e., reduced leakagepower and lower supply power Vdd) digital integrated circuitapplications that employ Janus micro/nano-components (e.g., Janusparticles, cylinders, prisms, etc.—see below) and techniques for thefabrication thereof. In general, a Janus micro/nano-component is aparticle, cylinder, prism, etc. the surface of which has two (or more)distinct physical properties. For instance, as will be described indetail below, the Janus micro/nano-component could be composed of twodifferent materials. In order to form complementary devices/circuits,the present devices will employ complementary positively and negativelycharged Janus components the position and rotation of which iscontrolled by pairs of negatively and positively charged back gates. Aswill be described in detail below, electrical contact is formed in thedevices when the Janus components form a bridge between the device'ssource and drain contacts.

The use of Janus micro/nano-components in an electromechanical sensorhas several notable benefits: 1) Janus micro/nano-components-basedelectromechanical devices have a lower control gate voltage, 2) Janusmicro/nano-components-based electromechanical devices exhibit betterreliability than conventional electromechanical devices, 3) Janusmicro/nano-components-based electromechanical devices can be fabricatedat a lower cost than conventional electromechanical devices, and 4)Janus micro/nano-components-based electromechanical devices haveapplicability to bio-medical applications (e.g., bioswitches).

FIGS. 1A-D are three-dimensional diagrams illustrating exemplary Janusmicro/nano-components that may be used in accordance with the presenttechniques. There are currently three methods known for fabricatingJanus particles, cylinders, prisms, etc. See for example Lattuada etal., “Synthesis, properties and applications of Janus nanoparticles,”nanotoday, vol. 6, Issue 3, June 2011, pages 286-308 (hereinafter“Lattuada”), the contents of which are incorporated by reference herein.For instance as described in Lattuada, one method for fabricating Janusparticles is via self-assembly of block copolymers, and mixtures ofligands on the surfaces of the nanoparticles. Another method forfabricating Janus particles is through a masking step in which particlesare trapped at the interface between two phases, so that a modificationto the particle surface is made only on one side. Yet another method forfabricating Janus particles relies on the phase separation of twodifferent substances, usually either two polymers, or a polymer and aninorganic material.

According to an exemplary embodiment, the Janus micro/nano-componentsused in accordance with the present techniques include a first portionmade of a first material which is an electrically conducting material,such as a metal(s), and a second portion made of a second material whichis an electrically insulating material, such as a dielectric material(e.g., an oxide or nitride dielectric material). See for example FIG. 1Awhich depicts an exemplary Janus particle which may be used inaccordance with the present techniques. The Janus particle shown in FIG.1A has one hemisphere composed of a metal (in this case gold (Au)) and asecond hemisphere composed of a dielectric material (in this case anoxide dielectric material). Thus one portion of the particle iselectrically conductive and another portion is not electricallyconductive. Gold (Au) is an appropriate metal for use in the presentJanus components since it is relatively abundant and is biocompatible,however other metals may be employed. By way of example only, suitablemetals for use as the electrically conductive portion in the presentJanus components include, but are not limited to, gold (Au), copper(Cu), aluminum (Al), silver (Ag), and palladium (Pd).

As highlighted above, the geometries of the Janus micro/nano-components(also referred to herein generally as “Janus components”) are scalable.In the case of a Janus particle like that shown in FIG. 1A, thedimensions of the particle may be measured based on the diameter d ofthe particle. By way of example only, the Janus particle may have adiameter d of from about 20 nanometers (nm) to about 20 micrometers(pin). Further, when the Janus particle has a diameter d of from about100 nanometers (nm) to about 20 micrometers (m) it is considered hereinto be a Janus microcomponent and when the Janus particle has a diameterd of from about 20 nm to about 100 nm it is considered herein to be aJanus nanocomponent.

FIG. 1B is a diagram which depicts an exemplary Janus cylinder which maybe used in accordance with the present techniques. The Janus cylindershown in FIG. 1B is composed of a metal (in this case Au) along oneportion of its length and a dielectric material (in this case an oxidedielectric) along another portion of its length. Thus one portion of thecylinder is electrically conductive and another portion is notelectrically conductive. As provided above, in addition to Au, othersuitable metals for forming the electrically conductive portion of theJanus component include, but are not limited to, Cu, Al, Ag, and Pd.

The dimensions of the Janus cylinder shown in FIG. 1B may be measuredbased on the length L of the cylinder. By way of example only, the Januscylinder may have a length L of from about 20 nm to about 100 μm.Further, when the Janus cylinder has a length L of from about 100 nm toabout 100 μm it is considered herein to be a Janus microcomponent andwhen the Janus cylinder has a length L of from about 20 nm to about 100nm it is considered herein to be a Janus nanocomponent.

FIG. 1C is a diagram which depicts another exemplary Janus cylinderwhich may be used in accordance with the present techniques. Bycomparison with the Janus cylinder shown in FIG. 1B, this Janus cylinderis composed of a metal (in this case Au) along (the entire length of)one side of the cylinder and a dielectric material (in this case anoxide dielectric material) along (the entire length of) another side ofthe cylinder. Thus one side of the cylinder is electrically conductiveand another side is not electrically conductive. Exemplary Januscylinder dimensions were provided above. Gold (Au) is being used heremerely as an example. As provided above, in addition to Au, othersuitable metals for forming the electrically conductive portion of theJanus component include, but are not limited to, Cu, Al, Ag, and Pd.

FIG. 1D is a diagram which depicts an exemplary Janus prism which may beused in accordance with the present techniques. The Janus prism shown inFIG. 1D has one portion composed of a metal (in this case Au) and asecond portion composed of a dielectric material (in this case an oxidedielectric material). Thus one portion of the prism is electricallyconductive and another portion is not electrically conductive. FIG. 1Dalso illustrates that the conductive and non-conductive portions of theJanus component do not have to be the same size. For instance in theexamples shown in FIGS. 1A-C, the metal and oxide portions are shown tobe the same size as one another. In the example shown in FIG. 1D, themetal portion makes up only one side of the prism while the remainder ofthe prism is the oxide. Again, gold (Au) is being used here merely as anexample. As provided above, in addition to Au, other suitable metals forforming the electrically conductive portion of the Janus componentinclude, but are not limited to, Cu, Al, Ag, and Pd.

The dimensions of the Janus prism shown in FIG. 1D may be measured basedon the length L, width W and height H of the prism. By way of exampleonly, the Janus prism may have a length L, width W and height H each offrom about 20 nm to about 20 μm. Further, when the Janus prism has alength L, width W, and height H each of from about 100 nm to about 20 μmit is considered herein to be a Janus microcomponent and when the Janusprism has a length L, width W, and height H each of from about 20 nm toabout 100 nm it is considered herein to be a Janus nanocomponent.

As highlighted above, complementary Janus components are used herein toform devices and circuits, wherein one (or more) of the Janus componentsin the device is/are positively charged and one (or more) other of theJanus components in the device is/are negatively charged. To do so, afixed (positive or negative) charge is created on the surface of themetal portion and/or on the surface of the dielectric portion of theJanus components.

More specifically, a fixed negative charge can be created on the surfaceof the dielectric portions of the Janus components using a moleculecontaining a hydroxamic group:

and negatively charged functional groups (e.g., pyridine groups). See,for example, FIG. 2. A hydroxamic group is preferred for anchoring themolecules to a dielectric (e.g., oxide or nitride) surface. Thus, by wayof the hydroxamic group, the molecules will self-assemble on the surfaceof the dielectric portions of the Janus components forming a(self-assembled) monolayer on those dielectric surfaces bearing anegative charge. Selective modification of a Janus component isdescribed for example in Roh et al., “Biphasic Janus particles withnanoscale anisotropy,” Nature Materials, vol. 4 (October 2005) (whichdescribes, for example, biphasic jetting) and in Perro et al., “Designand synthesis of Janus micro- and nanoparticles,” J. Mater. Chem., 15,3745-3760 (2005) (which describes for example surface modification ofpartially-masked particles), the contents of each of which isincorporated by reference herein.

In the same manner, a fixed positive charge can be created on thesurface of the dielectric portions of the Janus components using amolecule containing a hydroxamic group and positively charged functionalgroups (e.g., diazonium groups). See, for example, FIG. 3. As providedabove, based on the affinity of the hydroxamic group for reaction with adielectric (e.g., oxide or nitride), the molecules will self-assemble onthe surface of the dielectric portions of the Janus components forming a(self-assembled) monolayer on those dielectric surfaces bearing apositive charge.

To form a fixed (positive or negative) charge selectively on thesurfaces of the metal portions of the Janus components, the same(positively or negatively charged) functional groups can be employed,but another group is needed to anchor the molecule to the metal surface.A suitable anchoring group for a metal surface is a thiol (—SH).Specifically, a fixed negative charge can be created on the surface ofthe metal portions of the Janus components using a molecule containing athiol group and negatively charged functional groups (e.g., pyridinegroups). Based on the affinity of the thiol group for reaction with ametal (e.g., gold), the molecules will self-assemble on the surface ofthe metal portions of the Janus components forming a (self-assembled)monolayer on those dielectric surfaces bearing a negative charge.

Similarly, a fixed positive charge can be created on the surface of themetal portions of the Janus components using a molecule containing athiol group and positively charged functional groups (e.g., diazoniumgroups). Based on the affinity of the thiol group for reaction with ametal (e.g., gold), the molecules will self-assemble on the surface ofthe metal portions of the Janus components forming a (self-assembled)monolayer on those dielectric surfaces bearing a positive charge.Techniques for creating a fixed charge on a Janus component aredescribed, for example, in U.S. patent application Ser. No. 13/665,334filed on Oct. 31, 2012, entitled “Techniques for Fabricating Janus MEMSTransistors,” (hereinafter “U.S. patent application Ser. No.13/665,334”) the contents of which are incorporated by reference herein.

As highlighted above, in order to form a complementary device/circuit,at least one of the Janus components has to have a fixed positive chargeon a portion of its surface and at least one other Janus component hasto have a fixed negative charge on a portion of its surface. Given theabove-described process, it is apparent that according to the presenttechniques, this combination of positively and negatively charged Januscomponents can be achieved in a number of different ways. For instance,one may simply create a fixed positive charge on the surface of thedielectric portion of one or more of the Janus components, and a fixednegative charge on the surface of the dielectric portion of one or moreother of the Janus components. The same process outlined above couldinstead be used to create positive/negative charges on the surfaces ofthe metal portions of the Janus components. Further, any combination ofpositively charged/negatively charged/uncharged metal/dielectricsurfaces may be employed as long as: i) a portion (dielectric or metal)of each of the Janus components has a fixed (positive or negative)charge (while the other portion (dielectric or metal) has the oppositecharge or no fixed charge), and ii) at least one of the Janus componentshas a fixed (positive or negative) charge that is opposite to the fixed(positive or negative) charge on at least one other Janus component. Touse a simple example where two Janus components are present in thedevice: having one of (the two) Janus components with a fixed positivecharge on the surface of the dielectric portion, and the other of (thetwo) Janus components with a fixed negative charge on the surface of thedielectric portion would meet conditions i and ii. However, as providedbelow, configurations are considered herein where more than two Januscomponents are used in the device, e.g., as stacks of components.

The fixed charges on the Janus particles permits the Janus components tobe actuated (e.g., turned/moved) during operation of the transistordevice in response to an applied gate electrical field. The fact thatcharges of opposite polarity are employed on the components means thatthe Janus components will react differently to the same applied gatevoltage. See for example FIG. 4 which is an exemplary relay deviceaccording to the present techniques. In this example, the relay containstwo complementary Janus components, one having a fixed positive chargeand one having a fixed negative charge—with the charges being present onthe surface of the same (dielectric or metal) portion in both of theJanus components. In accordance with FIGS. 1A-D, the darker surface is(arbitrarily) used herein to represent the metal portion of thecomponent and thus, in FIG. 4, it can be assumed that a fixed negativesurface charge has been formed on the surface of the metal portion ofone of the two components and a fixed positive surface charge has beenformed on the surface of the metal portion of the other component. It isalso notable that while FIG. 4 depicts Janus particles, any of the otherJanus component shapes (e.g., cylinders, prisms, etc.—as describedabove) can be employed in the same manner as shown.

As shown in FIG. 4, the opposite charges on the two components willresult in the components turning/moving differently in response to anapplied gate voltage (Vin). Thus, when a negative back gate voltage(Vin<0) is applied, the configuration shown in FIG. 4 is the result.Namely, the positively charged Janus component will actuate (i.e.,rotate) its positively charged surface toward the back gate, and thenegatively charged Janus component will actuate (i.e., rotate) itsnegatively charged surface away from the back gate. In the configurationshown, this would result in continuity between the supply voltage (Vdd)and the Vout via the metal portion of the positively charged Januscomponent. Conversely, if a positive back gate voltage (Vin>0) wasapplied, then the Janus components would rotate with the positivelycharged Janus component positioning its positively charged surfacefacing away from the back gate (not shown). This would position thedielectric portion of the positively charged Janus component between theVdd and the Vout, thus breaking the continuity between the Vdd and theVout. Further, by using complementary Janus components, one of thecomponents is always in a non-conducting position (i.e., the dielectricportion is positioned between the Vdd and the Vout) and thus (like aCMOS circuit) the present device draws significant power onlymomentarily during switching.

An exemplary method for fabricating the present complementary Januscomponent device is now presented by way of reference to FIGS. 5-14.First, the back gates of the device are formed. See FIG. 5. The startingplatform for the fabrication process is a substrate 502 which can be astandard glass, metal, plastic, etc. substrate, or a semiconductor wafer(e.g., bulk semiconductor, silicon-on-insulator (SOI), etc.).

A dielectric layer 504 is then formed on the substrate 502. Layer 504can be formed from any suitable dielectric material, including but notlimited to, oxide and/or nitride materials. According to an exemplaryembodiment, dielectric layer 504 is formed having a thickness of fromabout 100 nanometer (nm) to about 10 micrometers (μm). Next, an N-typeback gate 506 n and a P-type back gate 506 p of the device are formed ondielectric layer 504.

The back gates 506 n and 506 p can be formed from any suitableconductive gate material, including but not limited to, dopedpoly-silicon, metal(s), etc. According to an exemplary embodiment, theback gates 506 n and 506 p are formed by depositing a dielectric layer508 on dielectric layer 504, patterning dielectric layer 508 withtrenches corresponding to the footprint and location of the back gates506 n and 506 p, and filling the trenches with a metal (such as copper),poly-silicon, etc. to form the back gates 506 n and 506 p. Any excessgate material can be removed using, e.g., chemical-mechanical polishing(CMP). Further, while the dielectric 504 and dielectric 508 may beformed from the same material, it may be advantageous to form thedielectric 504 and dielectric 508 from different materials, such as anoxide and a nitride (or vice-a-versa), respectively, so as to permit anetch selectivity between the layers during patterning of the trenches.

An etch stop layer 602 is then formed over and covering the back gates506 n and 506 p. See FIG. 6. The etch stop layer 602 will be used laterin the process during the anchor trench formation (i.e., to form thetrenches into which the Janus components are placed). The etch stoplayer will also serve as a dielectric between the Janus components andthe back gates 506 n and 506 p. Accordingly, the etch stop layer ispreferably formed from a nitride or oxide dielectric material. By way ofexample only, the etch stop layer 602 can be deposited using a processsuch as chemical vapor deposition (CVD) to a thickness of from about 10nm to about 100 nm.

Next, as shown in FIG. 7, electrodes 702 are formed over the back gates.An exemplary configuration of the electrodes 702 (i.e., includingsource, drain and gate electrodes) is shown in FIG. 8, described below.The formation of the electrodes 702 follows an analogous process to thatdescribed above for forming the back gates. Namely, a dielectric layer704 is first deposited on the etch stop layer 602, the dielectric layer704 is patterned with the corresponding footprint and location of theelectrodes 702, and the pattern is filled with a conductive material,such as a metal (e.g., copper), poly-silicon, etc. to form theelectrodes 702. Any excess conductive material can be removed using,e.g., CMP. Further, as provided above, the etch stop layer 602 ispreferably formed from a dielectric material. While the dielectricmaterial used for the etch stop layer 602 may be the same as that usedfor the dielectric layer 704, it may be advantageous to form thedielectric layer 704 from a different material from the etch stop layer602, such as an oxide and a nitride (or vice-a-versa), respectively, soas to permit an etch selectivity between the layers during patterning ofthe dielectric layer 704 to form the electrodes 702, and later to formthe anchor trenches—see below.

An exemplary configuration of the electrodes 702 is shown by way of atop-down view of the device presented in FIG. 8. The depiction shown inFIG. 8 is from viewpoint A (see FIG. 7). As shown in FIG. 8, in thisexemplary configuration, the electrodes 702 are patterned to form twosets of gate (G1 and G2) and source and drain (S and D) electrodes 702,each set corresponding to one of the (two) complementary Janus componentdevices. As shown in FIG. 8, there are gaps between each pair of source(S) and drain (D) electrodes, and the gate electrodes (G1 and G2) arelocated adjacent to the gaps—perpendicular to the source and drainelectrodes (i.e., thus if the source and drain electrodes are aligned onthe surface of the device along an x-direction, with the gapstherebetween, then the gate electrodes are located on the surface of thedevice, adjacent to the gaps, along a y-direction, see FIG. 8). Theabove-described Janus component(s) will be positioned in the gaps.Further, the gaps are angled such that when the metal portion of theJanus component(s) in the gap are facing the gate electrode G1, there iscontinuity between the source (S) and the drain (D) electrodes.Conversely, when the dielectric portion of the Janus component(s) in thegap are facing the gate electrode G1, there is no continuity between thesource (S) and the drain (D) electrodes. Namely, the angled gap ensuresthat the desired portion of the Janus component (metal or dielectric)makes contact with the source (S) and the drain (D) electrodes. Thisaspect will become apparent in the description to follow. It is notablethat what is shown in FIG. 7 is a cross-sectional cut along line B-B′ inFIGS. 8-10.

Another exemplary configuration of the electrodes 702 is shown by way ofa top-down view of the device presented in FIG. 9. Again the depictionshown in FIG. 9 is from viewpoint A (see FIG. 7). The electrodeconfiguration shown in FIG. 9 can, for example, be employed to form adouble input/output inverter device.

As shown in FIG. 9, in this exemplary configuration, the electrodes 702are patterned to form two sets of gate (G1 and G2) and four sets ofsource and drain (S and D) electrodes 702. As compared to the designshown in FIG. 8, the extra set of source and drain (S and D) electrodesin FIG. 9 permits dual input/output operation. As will be described indetail below, a dual input/output device is applicable in situationswhere each of the Janus components have both positive and negativecharged surfaces, such that one (positive or negative) charged surfaceinteracts with one set of the source (S) and drain (D) electrodes while(at the same time) the other (positive or negative) charged surfaceinteracts with the other (complementary) set of source (S) and drain (D)electrodes. By comparison, the design shown in FIG. 8 can be operatedusing Janus components having either one or two charged surfaces. Thisdistinction will become further apparent from the description below.

Yet another exemplary configuration of the electrodes 702 is shown byway of a top-down view of the device presented in FIG. 10. Again thedepiction shown in FIG. 10 is from viewpoint A (see FIG. 7). Like thedesign of FIG. 8, the electrode configuration shown in FIG. 10 can, forexample, be employed to form a single input/output inverter device.

As shown in FIG. 10, in this exemplary configuration, the electrodes 702are patterned to form two gates (G) and two sets of source and drain (Sand D) electrodes 702. The configuration in FIG. 10 is a simplifiedversion of the single input/output device of FIG. 8. Namely, bycomparison with the design of FIG. 8, the configuration in FIG. 10employs only a single gate electrode (G) for each complementary Januscomponent device. While the designs shown in FIGS. 8 and 10 operate inthe same manner as a single input/output device, simplifying the designdecreases manufacturing complexity and production costs.

Whichever electrode 702 configuration is employed, the generalfabrication process proceeds in the same manner as now described.Namely, as shown in FIG. 11, anchor trenches 1102 are formed in thedielectric layer 704 between the electrodes 702. By way of reference toFIGS. 8-10, the anchor trenches are formed between the source (S) andthe drain (D) electrodes. For illustrative purposes, the placement ofthe anchor trenches 1102 is shown outlined in a dashed pattern in FIGS.8-10.

According to an exemplary embodiment, the anchor trenches 1102 areformed using standard lithography and etching techniques wherein a mask(not shown) is formed on the dielectric layer 704 patterned with thefootprint and location of the anchor trenches 1102. A dielectricreactive ion etching (RIE) step can then be used to etch the anchortrenches in the dielectric layer 704. As provided above, the dielectriclayer 704 is preferably formed from a different material than the etchstop layer 602, such as an oxide and a nitride (or vice-a-versa), toprovide etch selectivity between the materials. The dimensions of theanchor trench will depend on the dimensions of the particular Januscomponents being used and whether one or more Janus components will beanchored in the trench—see below description of multi-componentembodiments. However, as shown in FIG. 11, it is preferable that aborder of dielectric material 704 is left between the edge of the anchortrenches and the electrodes 702.

The Janus particles are then introduced onto the device. As providedabove, each device will employ complementary Janus particles. In thesimplest case, this includes placing at least one Janus component havinga portion (metal or dielectric) with a fixed positive charge and oneJanus component having a portion (metal or dielectric) with a fixednegative charge. In that case, a ‘chemical approach’ may be used toplace the Janus components, wherein the device is soaked in an aqueoussolution containing the Janus components.

According to an exemplary embodiment, an electrical field is applied toone of the two back gates while the device is soaked in solutionscontaining the Janus components. For instance, as illustrated in FIG.12, the device can be soaked in a first solution containing Januscomponents with a fixed positive charge, while a negative gate voltage(V<0) is applied to one of the back gates 506 n. See FIG. 12.Accordingly, the fixed positive charge on the particles in the solutionwill be attracted to the negative charge applied to back gate 506 n. Theanchor trench 1102 (as shown in FIG. 12) in the n-type transistor willserve to physically restrain the Janus component(s) that are depositedin this manner. Alternatively, instead of soaking the device in theJanus component solution, the solution can also be spin-coated onto thesurface of the device.

Next, the process can be repeated to deposit a Janus component(s) in thecomplementary p-type transistor. Here, the device would be soaked in asecond solution containing Janus components with a fixed negativecharge, while a positive gate voltage (V>0) is applied to the other backgate 506 p. See FIG. 13. Accordingly, the fixed negative charge on theparticles in the solution will be attracted to the positive chargeapplied to back gate 506 p. The anchor trench 1102 (as shown in FIG. 12)in the p-type transistor will serve to physically restrain the Januscomponent(s) that are deposited in this manner. In the example shown inthe figures, the Janus components used are Janus particles. However, anyof the other Janus component geometries described herein can be employedin the same manner. Alternatively, instead of soaking the device in theJanus component solution, the solution can also be spin-coated onto thesurface of the device.

This chemical approach can also be used to deposit Janus componentshaving fixed charges on both the surface of the dielectric and metalportions of the component. By way of example only, a first aqueoussolution containing Janus components with a fixed positive charge on thedielectric portion and a fixed negative charge on the metal portion canbe contacted with the device (through soaking, spin-coating, etc.) whilea negative gate voltage is applied to back gate 506 n—which will depositthe components in the n-type transistor in the same manner as depictedin FIG. 12. Next, a second aqueous solution containing Janus componentswith a fixed negative charge on the dielectric portion and a fixedpositive charge on the metal portion can be contacted with the device(through soaking, spin-coating, etc.) while a positive gate voltage isapplied to back gate 506 p—which will deposit the components in thep-type transistor in the same manner as depicted in FIG. 13.

In an alternate embodiment, rather than using a ‘chemical approach,’ theJanus components can be placed in the device using a geometric approachwherein the above-described (first, second) aqueous solutions containingthe particular charged Janus components are contacted (soaked,spin-coated, etc.) with the device through a patterned mask—for examplea photoresist, is placed over the transistor, and patterned to permitdeposition of at least one Janus component at the proper location foreach of the transistors.

With whatever approach is implemented, following placement of the Januscomponents in the device, the wafer may be rinsed (for example withdistilled water) to remove extra deposited Janus components, and thephotoresist (if present) can be removed by conventional processes. Asdescribed above, the anchor trenches serve to ‘anchor’ the Januscomponents in place during this rinsing step.

Finally, an optional liquid coating 1402 can be depositedover/surrounding the device, covering the Janus components. See FIG. 14.The liquid coating 1402 serves as an insulator and prevents arcingbetween the electrodes. The liquid coating 1402 may also be referred toherein as a “liquid packaging,” and may be formed from an oil-basedmedia (such as a commercially available highly refined transformer oilthat is free of water vapor) or an insulating liquid. Fabrication of theJanus component-based device may now be considered complete.

It is notable that the back gates 506 n and 506 p serve primarily duringfabrication to place the Janus components in the proper locations, asdescribed immediately above. The electrodes 702 (of the variousconfigurations presented herein) are used to operate the device. FIGS.15-17 illustrate operation of the different present deviceconfigurations.

For example, FIGS. 15A-B are top-down diagrams illustrating the singleinput/output electrode configuration of FIG. 8. The depictions shown inFIGS. 15A-B are from viewpoint C (see FIG. 14). For ease of depiction,the optional liquid coating 1402 is not shown. Assume for this examplethat only the surfaces of the dielectric portion of the Janus componentshave a fixed (positive or negative) charge. Thus, the portions of theJanus components labeled with a charge are the dielectric portions. Asshown in FIG. 15A, when a positive gate voltage is applied to the gateelectrodes G1 and a complementary negative gate voltage is applied tothe gate electrodes G2, the Janus component(s) in the p-type transistorwill rotate such that the negatively charged (dielectric) surfaces ofthose components face the corresponding gate electrode G1—such that thedielectric portion of the Janus component(s) is present between thesource (S) and the drain (D) electrodes in the p-type transistor andthus there is no continuity between these electrodes in the p-typetransistor. The Janus component(s) in the n-type transistor will rotatesuch that the positively charged (dielectric) surfaces of thosecomponents face away from the corresponding gate electrode G1—such thatthe metal portion of the Janus component(s) is present between thesource (S) and the drain (D) electrodes in the n-type transistor andthus there is continuity between these electrodes in the n-typetransistor. In this state, the output (Vout) read through the source (S)and drain (D) electrodes is at low voltage state since there is nocontinuity between the Vdd and the output (but there is continuitybetween the Vss and the output). By comparison, as will be describedbelow, the output is at a high voltage state when the device is switchedand there is continuity between the Vdd and the output (and nocontinuity between the Vss and the output).

However, as shown in FIG. 15B, when a negative gate voltage is appliedto the gate electrode G1 and a complementary positive gate voltage isapplied to the gate electrodes G2, the Janus component(s) in the p-typetransistor will rotate such that the negatively charged (dielectric)surfaces of those components face away from the corresponding gateelectrode G1—such that the metal portion of the Janus component(s) ispresent between the source (S) and the drain (D) electrodes in thep-type transistor and thus there is continuity between these electrodesin the p-type transistor. The Janus component(s) in the n-typetransistor will rotate such that the positively charged (dielectric)surfaces of those components face the corresponding gate electrodeG1—such that the dielectric portion of the Janus component(s) is presentbetween the source (S) and the drain (D) electrodes in the n-typetransistor and thus there is no continuity between these electrodes inthe n-type transistor. In this state, the output (Vout) read through thesource (S) and drain (D) electrodes is at high voltage state since thereis now continuity between the Vdd and the output.

FIGS. 16A-B are top-down diagrams illustrating the double input/outputelectrode configuration of FIG. 9. The depictions shown in FIGS. 16A-Bare from viewpoint C (see FIG. 14). For ease of depiction, the optionalliquid coating 1402 is not shown. Assume for this example that only thesurfaces of the dielectric portion of the Janus components have a fixed(positive or negative) charge. Thus, the portions of the Januscomponents labeled with a charge are the dielectric portions. As shownin FIG. 16A, when a positive gate voltage is applied to the gateelectrodes G1 and a complementary negative gate voltage is applied tothe gate electrodes G2, the Janus component(s) in the p-type transistorwill rotate such that the negatively charged (dielectric) surfaces ofthose components face the corresponding gate electrode G1—such that i)the dielectric portion of the Janus component(s) is present between thefirst set of source (S1) and the drain (D1) electrodes in the p-typetransistor and thus there is no continuity between these electrodes inthe p-type transistor, and ii) the metal portion of the Januscomponent(s) is present between the second set of source (S2) and thedrain (D2) electrodes in the p-type transistor and thus there iscontinuity between these electrodes in the p-type transistor. The Januscomponent(s) in the n-type transistor will rotate such that thepositively charged (dielectric) surfaces of those components face awayfrom the corresponding gate electrode G1—such that i) the metal portionof the Janus component(s) is present between the first set of source(S1) and the drain (D1) electrodes in the n-type transistor and thusthere is continuity between these electrodes in the n-type transistor,and ii) the dielectric portion of the Janus component(s) is presentbetween the second set of source (S2) and the drain (D2) electrodes inthe n-type transistor and thus there is no continuity between theseelectrodes in the n-type transistor. In this state, i) the output (Vout)read through the first set of source (S1) and drain (D1) electrodes is 0since there is no continuity between the Vdd and the output through S1and D1, and ii) the complementary output (−Vout) read through the secondset of source (S2) and drain (D2) electrodes is at a high voltage state(−Vss) since there is continuity between the −Vss and the output throughS2 and D2.

However, as shown in FIG. 16B, when a negative gate voltage is appliedto the gate electrode G1 and a complementary positive gate voltage isapplied to the gate electrodes G2, the Janus component(s) in the p-typetransistor will rotate such that the negatively charged (dielectric)surfaces of those components face away from the corresponding gateelectrode G1—such that i) the metal portion of the Janus component(s) ispresent between the first set of source (S1) and the drain (D1)electrodes in the p-type transistor and thus there is continuity betweenthese electrodes in the p-type transistor, and ii) the dielectricportion of the Janus component(s) is present between the second set ofsource (S2) and the drain (D2) electrodes in the p-type transistor andthus there is no continuity between these electrodes in the p-typetransistor. The Janus component(s) in the n-type transistor will rotatesuch that the positively charged (dielectric) surfaces of thosecomponents face the corresponding gate electrode G1—such that i) thedielectric portion of the Janus component(s) is present between thefirst set of source (S1) and the drain (D1) electrodes in the n-typetransistor and thus there is no continuity between these electrodes inthe n-type transistor, and ii) the metal portion of the Januscomponent(s) is present between the second set of source (S2) and thedrain (D2) electrodes in the n-type transistor and thus there iscontinuity between these electrodes in the n-type transistor. In thisstate, i) the output (Vout) read through the first set of source (S1)and drain (D1) electrodes is positive since there is continuity betweenthe Vdd and the output through S1 and D1, and ii) the output (Vout) readthrough the second set of source (S2) and drain (D2) electrodes isnegative since there is continuity between the input −Vdd and the outputthrough S2 and D2.

FIGS. 17A-B are top-down diagrams illustrating the single input/outputelectrode configuration of FIG. 10. The depictions shown in FIGS. 17A-Bare from viewpoint C (see FIG. 14). For ease of depiction, the optionalliquid coating 1402 is not shown. Assume for this example that thesurfaces of the dielectric portion of the Janus components have a fixed(positive or negative) charge and the surfaces of the metal portions ofthe Janus components also have a fixed (positive or negative) charge,and wherein the surfaces of the dielectric and metal portions have anopposite charge from one another. To illustrate this configuration, inFIGS. 17A and 17B, the charge on the dielectric surfaces of the Januscomponents is shown in bold and the charge on the metal surface of theJanus components is shown in regular (unbold) text. Thus, the portionsof the Janus components labeled with a charge in bold are the dielectricportions. As shown in FIG. 17A, when a positive gate voltage is appliedto the gate electrodes G1, the Janus component(s) in the p-typetransistor will rotate such that the negatively charged (dielectric)surfaces of those components face (and the positively charged (metal)surfaces of those components face away from) the corresponding gateelectrode G1—such that the dielectric portion of the Janus component(s)is present between the source (S) and the drain (D) electrodes in thep-type transistor and thus there is no continuity between theseelectrodes in the p-type transistor. The Janus component(s) in then-type transistor will rotate such that the positive charged(dielectric) surfaces of those components face away from (and thenegatively charged (metal) surfaces of those components face) thecorresponding gate electrode G1—such that the metal portion of the Januscomponent(s) is present between the source (S) and the drain (D)electrodes in the n-type transistor and thus there is continuity betweenthese electrodes in the n-type transistor. In this state, the outputread through the source (S) and drain (D) electrodes is at a low voltagestate since there is no continuity between the Vdd and the output, andthere is continuity between the Vss and the output.

However, as shown in FIG. 17B, when a negative gate voltage is appliedto the gate electrodes G1, the Janus component(s) in the p-typetransistor will rotate such that the positively charged (metal) surfacesof those components face (and the negatively charged (dielectric)surfaces of those components face away from) the corresponding gateelectrode G1—such that the metal portion of the Janus component(s) ispresent between the source (S) and the drain (D) electrodes in thep-type transistor and thus there is continuity between these electrodesin the p-type transistor. The Janus component(s) in the n-typetransistor will rotate such that the negatively charged (metal) surfacesof those components face away from (and the positively chargeddielectric surfaces of those components will face) the correspondinggate electrode G1—such that the dielectric portion of the Januscomponent(s) is present between the source (S) and the drain (D)electrodes in the n-type transistor and thus there is no continuitybetween these electrodes in the n-type transistor. In this state, theoutput read through the source (S) and drain (D) electrodes is at highvoltage state since there is now continuity between the Vdd and theoutput.

As provided above, any of the Janus component geometries describedherein may be used in any of the device configurations shown. Further, asingle or multiple Janus components may be used in each of the (n-typeand p-type) Janus transistors described herein. The implementation of asingle Janus particle in each (n-type or p-type) transistor wasdemonstrated in FIGS. 15-17. It is also possible to employ multipleJanus particles in a given (n-type or p-type) transistor which functionin the same manner as a single component. The multiple Janus particlescan be implemented in series (see FIG. 18) or in parallel (see FIG. 19).

FIG. 18 is a diagram illustrating multiple Janus particles connected inseries in each (n-type or p-type) transistor. For illustrative purposesonly, the single input/output electrode configuration of FIG. 10 isshown. Due to the shape of the (spherical) Janus particles shown in FIG.18, it may be desirable to form a metal bridge in between the source anddrain electrodes to ensure that continuity will be achieved between theparticles. Specifically, due to the spherical shape of the particles,the amount of surface area available for contact between the particlesis small. The metal bridge increases this contact area. While only onemetal bridge is shown in FIG. 18, it is to be understood that multiplemetal bridges may be employed to ‘bridge’ the gap between Janusparticles—depending on how many Janus particles are present with onebridge being present between each pair of particles. For instance, ifthree Janus particles were employed in series, then two metal bridgeswould preferably be employed. According to an exemplary embodiment, themetal bridge(s) is/are formed (from Cu) at the same time as theformation of the electrodes 702.

As described above, the spherical shape of the Janus particles limitsthe contact area between particles (in the case of multiple particles inseries), thus making use of a metal bridge (as shown in FIG. 18)preferable. By contrast, when the Janus components are cylindrical orprism-shaped, then the use of a metal bridge is likely unnecessary.

The multiple Janus components (in series) may be anchored using oneanchor trench, or multiple anchor trenches wherein each anchor trenchanchors at least one Janus component. For illustrative purposes only, asingle anchor trench is shown in FIG. 18 in conjunction with the n-typetransistor, and multiple anchor trenches are shown in FIG. 18 inconjunction with the p-type transistors. This is done to illustrate howeither single or multi-trench configuration may be used, however it islikely for production purposes that one configuration (single ormulti-trench) would be selected and implemented for both (n-type andp-type) transistors. The use of multiple Janus components (in series andin parallel) in a transistor device is also described in U.S. patentapplication Ser. No. 13/665,334.

When multiple Janus components are used in parallel (versus in series),as shown in FIG. 19, the anchor trench is made deeper to accommodate astack of multiple components. For illustrative purposes only, FIG. 19 isa derivation of FIG. 13 showing multiple Janus components in parallel.In this exemplary configuration, a thicker dielectric layer 508 isemployed and the anchor trenches have a greater depth d than in theother embodiments shown and described above. The depth of the trenchesis dependent on the particular type and shape of the Janus componentsbeing employed. Exemplary dimensions for the various types of Januscomponents were provided above. By way of example only, in onenon-limiting example, up to 10 Janus components (e.g., from 1 to 3 Januscomponents) are placed in series in the device. In the example shown inFIG. 19, 4 Janus components (in this case (spherical) Janus particles)are employed in parallel. It is apparent from FIG. 19 that the Januscomponents are physically constrained within the anchor trench, and willself align as a stack when deposited into the trench (in the same manneras described above). The switching operation of the device is the sameas the single component embodiment, except that in FIG. 19 thecomponents are rotated (and potentially translated—see below) togetheras a stack. Otherwise the operation is identical between the single- andmulti-component configurations.

Like the Janus particles, the Janus cylinders of FIG. 1C also functionto switch the device by rotating based on the applied gate voltage. SeeFIG. 20. Again, for illustrative purposes only, the electrode 702configuration of FIG. 10 is being used as an example. As with FIG. 17,assume for this example that the surfaces of the dielectric portion ofthe Janus components have a fixed (positive or negative) charge and thesurfaces of the metal portions of the Janus components also have a fixed(positive or negative) charge, and wherein the surfaces of thedielectric and metal portions have an opposite charge from one another.To illustrate this configuration, the charge on the dielectric surfacesof the Janus components is shown in bold and the charge on the metalsurface of the Janus components is shown in regular (unbold) text. Thus,the portions of the Janus components labeled with a charge in bold arethe dielectric portions.

For some of the other Janus component geometries considered herein, theJanus components actuate/slide within the trenches (rather thanrotating). See, for example, FIG. 21 which depicts operation of thepresent complementary Janus component device employing the Januscylinders of FIG. 1B and FIG. 22 which depicts operation of the presentcomplementary Janus component device employing the Janus prisms of FIG.1D. Again, as with FIG. 17, assume for this example that the surfaces ofthe dielectric portion of the Janus components have a fixed (positive ornegative) charge and the surfaces of the metal portions of the Januscomponents also have a fixed (positive or negative) charge, and whereinthe surfaces of the dielectric and metal portions have an oppositecharge from one another. To illustrate this configuration, the charge onthe dielectric surfaces of the Janus components is shown in bold and thecharge on the metal surface of the Janus components is shown in regular(unbold) text. Thus, the portions of the Janus components labeled with acharge in bold are the dielectric portions. These other Janus componentgeometries are also described in U.S. patent application Ser. No.13/665,334.

As shown in FIGS. 21 and 22, a positive gate voltage will attract/repelthe negative/positive charged surface of the Janus components. This willcause the Janus components to slide within the anchor trenches. As aresult, the metal portion of the Janus components will either bepresent/or actuate (moved) away from between the source and drainelectrodes.

Although illustrative embodiments of the present invention have beendescribed herein, it is to be understood that the invention is notlimited to those precise embodiments, and that various other changes andmodifications may be made by one skilled in the art without departingfrom the scope of the invention.

What is claimed is:
 1. A method of fabricating an electromechanicaldevice, the method comprising the steps of: forming a first back gateand a second back gate on a first dielectric layer over a substrate;forming an etch stop layer covering the first back gate and a secondback gate; forming electrodes in a second dielectric layer on the etchstop layer over the first back gate and the second back gate, whereinthe electrodes comprise one or more gate electrodes, one or more sourceelectrodes and one or more drain electrodes, wherein gaps are presentbetween the source electrodes and the drain electrodes, and wherein thegate electrodes are located adjacent to the gaps, perpendicular to thesource and drain electrodes; and placing one or more Janus components ineach of the gaps between the source and drain electrodes, wherein eachof the Janus components includes a first portion comprising anelectrically conductive material and a second portion comprising anelectrically insulating material, and wherein i) either the firstportion or the second portion of the Janus components placed in a firstone of the gaps has a fixed positive surface charge and ii) either thefirst portion or the second portion of the Janus components placed in asecond one of the gaps has a fixed negative surface charge.
 2. Themethod of claim 1, wherein the substrate comprises a glass, metal, orplastic substrate.
 3. The method of claim 1, wherein the substratecomprises a semiconductor wafer.
 4. The method of claim 1, wherein thefirst back gate and the second back gate are formed from a conductivematerial selected from the group consisting of: a metal and dopedpolysilicon.
 5. The method of claim 1, wherein the electricallyconductive material is a metal.
 6. The method of claim 5, wherein themetal is selected from the group consisting of: gold, copper, aluminum,silver, and palladium.
 7. The method of claim 1, wherein theelectrically insulating material is a dielectric material.
 8. The methodof claim 1, wherein either a) the first portion of the Janus componentsplaced in the first one of the gaps has a fixed positive surface chargeand the second portion of the Janus components placed in the first oneof the gaps has a fixed negative surface charge, or b) the first portionof the Janus components placed in the first one of the gaps has a fixednegative surface charge and the second portion of the Janus componentsplaced in the first one of the gaps has a fixed positive surface charge.9. The method of claim 1, wherein either a) the first portion of theJanus components placed in the second one of the gaps has a fixedpositive surface charge and the second portion of the Janus componentsplaced in the second one of the gaps has a fixed negative surfacecharge, or b) the first portion of the Janus components placed in thesecond one of the gaps has a fixed negative surface charge and thesecond portion of the Janus components placed in the second one of thegaps has a fixed positive surface charge.
 10. The method of claim 1,wherein multiple Janus components are placed in each of the gaps betweenthe source and drain electrodes, and wherein the multiple Januscomponents are connected in series.
 11. The method of claim 1, whereinmultiple Janus components are placed in each of the gaps between thesource and drain electrodes, and wherein the multiple Janus componentsare connected in parallel.
 12. The method of claim 1, wherein theelectrodes comprise a first and a second set of the gate electrodes, anda first and a second set of the source and drain electrodes, wherein thefirst set of the gate electrodes, the first set of the source and drainelectrodes and the Janus components placed in the first one of the gapsform a first transistor, and wherein the second set of the gateelectrodes, the second set of the source and drain electrodes and theJanus components placed in the second one of the gaps form a secondtransistor.
 13. The method of claim 1, wherein the electrodes comprise afirst and a second set of the gate electrodes, and two first and twosecond sets of the source and drain electrodes, wherein the first set ofthe gate electrodes, the two first sets of the source and drainelectrodes and the Janus components placed in the first one of the gapsform a first transistor, and wherein the second set of the gateelectrodes, the two second sets of the source and drain electrodes andthe Janus components placed in the second one of the gaps form a secondtransistor.
 14. The method of claim 1, wherein the electrodes comprise afirst and a second one of the gate electrodes, and a first and a secondset of the source and drain electrodes, wherein the first gateelectrode, the first set of the source and drain electrodes and theJanus components placed in the first one of the gaps form a firsttransistor, and wherein the second gate electrode, the second set of thesource and drain electrodes and the Janus components placed in thesecond one of the gaps form a second transistor.
 15. A method ofoperating an electromechanical device, the method comprising the stepsof: providing the electromechanical device having: a first back gate anda second back gate on a first dielectric layer over a substrate; an etchstop layer covering the first back gate and a second back gate;electrodes formed in a second dielectric layer on the etch stop layerover the first back gate and the second back gate, wherein theelectrodes comprise one or more gate electrodes, one or more sourceelectrodes and one or more drain electrodes, wherein gaps are presentbetween the source electrodes and the drain electrodes, and wherein thegate electrodes are located adjacent to the gaps, perpendicular to thesource and drain electrodes; and one or more Janus components placed ineach of the gaps between the source and drain electrodes, wherein eachof the Janus components includes a first portion comprising anelectrically conductive material and a second portion comprising anelectrically insulating material, and wherein i) either the firstportion or the second portion of the Janus components placed in a firstone of the gaps has a fixed positive surface charge and ii) either thefirst portion or the second portion of the Janus components placed in asecond one of the gaps has a fixed negative surface charge; and applyinga gate voltage to the gate electrodes to move the Janus components so asto position either: a) the first portion of the Janus components placedin the first one of the gaps between a first set of the source and drainelectrodes and the second portion of the Janus components placed in thesecond one of the gaps between a second set of the source and drainelectrodes, or b) the second portion of the Janus components placed inthe first one of the gaps between the first set of the source and drainelectrodes and the first portion of the Janus components placed in thesecond one of the gaps between the second set of the source and drainelectrodes.